Melt-based patterning for electronic devices

ABSTRACT

The present invention provides methods and apparatus for melt-based patterning for electronic devices. It employs and provides processes and apparatus for fabricating an electronic device having a pattern formed on a surface by a deposition material. Further, the invention a process for fabricating semiconductors, organic light-emitting devices (OLEDs), field-effect transistors, and in particular high-resolution patterning for RGB displays. A process for fabricating an organic electronic device includes the steps of heating and applying a pressure to the deposition material to form a melt, and depositing the melted deposition material on the surface with a phase-change printing technique or a spray technique. The melted deposition material solidifies on the surface.

TECHNICAL FIELD

The present invention is related to a process for fabricating anelectronic device having a pattern formed on a surface by a depositionmaterial. Further, the invention is related to a process for fabricatinga field-effect transistor and in particular to high-resolutionpatterning for RGB displays.

BACKGROUND OF THE INVENTION

Organic electronic devices and in particular organic light-emittingdevices (OLEDs) are commonly manufactured as a sequence of layersdeposited on top of each other such as a first electrode on a supportingsubstrate, several organic and inorganic layers, and a second electrode.So far, OLED technology is lacking a high-resolution patterning methodfor RGB displays for small molecules. The deposition technologiesdeveloped for small molecules so far show limitations for massproduction of large-sized displays.

Conventionally, vacuum evaporation is employed as the physical vapordeposition method in forming the organic layers. A common method forpatterning of the organic layers e.g. for red, green, and blue emittingsub-pixels in a full-color display, is the shadow mask technique.However, this technique is limited in size, resolution of the panel, andthe individual fill-factor of the pixel. For example, shadow masktechnology becomes extremely complicated in particular for small featuresizes. The material deposition during the process requires regular maskcleaning steps which delay the manufacturing. Thermal expansion of themask during the deposition limits the precision and aperture ratio.Moreover, repeatedly necessary mask alignment is time consuming andreduces yield.

A method used for patterning polymer light-emitting devices is ink-jetprinting of dissolved polymers as described in U.S. Pat. No. 6,087,196.This method of dispensing a liquid solution is not suitable formulti-layer OLEDs based on small molecules because previously depositedlayers are re-dissolved and intermixed by the sequential deposition ofmultiple layers from different solutions. When small molecules areheated some of the small molecules sublime directly, while others firstmelt and then evaporate. Therefore a new way of depositing suchmolecules is needed. It follows that there is still a need in the artfor improved patterning of structures for the fabrication ofsemiconductor devices, sensors, biochips, and displays using organicand/or inorganic active or biological layers.

SUMMARY AND ADVANTAGES OF THE INVENTION

An aspect of the present invention is to provide methods and apparatusfor the fabrication of semiconductor devices, circuits, sensors,biological patterns, biochips, and monochrome and/or color displaysusing organic and/or inorganic active or biological layers. It involvesthe deposition of molecules, oligomers or nanoparticles by aphase-change printing or spray technique and the fabrication of organiclight-emitting devices (OLEDs), color displays and other semiconductordevices.

In an example embodiment of the present invention, there is provided aprocess for fabricating an electronic device having a pattern formed ona surface by a deposition material. The process comprises the steps ofheating and applying a pressure to the deposition material to form amelt, and depositing the melted deposition material on the surface witha phase-change printing technique or a spray technique. Thereby themelted deposition material solidifies on the surface, i.e. when itreaches the surface.

In an other example embodiment of the present invention, a field-effecttransistor, also referred to as a thin-film field-effect transistor, ismade by a process comprising the steps of forming source and draincontacts on a substrate; heating and applying a pressure to a depositionmaterial to form a melt, the deposition material comprising an organicsemiconducting material; depositing the melted deposition material ontothe substrate with the source and drain contacts by one of aphase-change printing technique, and a spray technique, wherein themelted deposition material solidifies on the substrate and forms anorganic semiconducting layer; forming an insulating layer on the organicsemiconducting layer; and forming a gate contact on the insulatinglayer.

It is also possible to form the source, drain, and gate contacts as wellas the insulating layer by the phase-change printing or spray technique.This has the advantage that the whole device can be fabricated by thedisclosed process.

DESCRIPTION OF THE DRAWINGS

Embodiments of the invention are described in detail below, by way ofexample only, with reference to the following schematic drawings, inwhich:

FIG. 1 illustrates a phase diagram of a one-component system;

FIGS. 2 a-c illustrate steps for forming a pattern on a surface bydeposition of a deposition material using a pressure chamber inaccordance with the present invention;

FIGS. 3 a, b show schematic illustrations of a formation of organiclight-emitting devices;

FIG. 3 c shows a schematic illustration of a formation of an RGBdisplay;

FIG. 5 shows a schematic illustration of a formation of a field-effecttransistor; and

FIG. 6 illustrates a printing principle.

The drawings are provided for illustrative purpose only and do notnecessarily represent examples of the present invention to scale.

DETAILED DESCRIPTION OF THE INVENTION

The present invention enables methods and apparatus for the fabricationof semiconductor devices, circuits, sensors, biological patterns,biochips, and monochrome and/or color displays using organic and/orinorganic active or biological layers. It includes the deposition ofmolecules, oligomers or nanoparticles by a phase-change printing orspray technique and the fabrication of organic light-emitting devices(OLEDs), color displays and other semiconductor devices.

In accordance with the present invention, there is provided an exampleof a process for fabricating an electronic device having a patternformed on a surface by a deposition material. The process comprises thesteps of heating and applying a pressure to the deposition material toform a melt, and depositing the melted deposition material on thesurface with a phase-change printing technique or a spray technique.Thereby the melted deposition material solidifies on the surface, i.e.when it reaches the surface.

In general, the present invention relates to a way of high-resolutionpatterning of layers, for example with organic molecules, by aphase-change printing technique, also referred to as wax or fusionprinting technique, for the use in semiconductor devices, sensors, orcolor displays. Also a spray technique utilizing a gas can be applied.Prior to deposition, the deposition material or a part thereof is heatedto the melting temperature in a pressure chamber utilizing the p-V (T)diagram and deposited onto a substrate or surface, e.g. a thin filmtransistor array for a full-color display. The deposition of the melteddeposition material can be performed by a thermal phase-change printingtechnique or a spray technique. The material solidifies immediately whenit hits the substrate. The deposition can be repeated to cast multiplelayers on top of each other. The steps of the process can be repeated todeposit multiple layers, i.e. more than three layers can be formedeasily. In a further example, the multiple layers can be formed bydepositing different deposition materials. The process allows acontrolled deposition of the materials and tailoring of thecharacteristics, e.g. by substrate heating/cooling, deposition in hotenvironment (gas), changing pressure etc. Further, the process is alsoideally suited for doped systems (mixing of liquids).

As indicated, the heating and applying of pressure can be performed in apressure chamber exploiting the pressure (P)/temperature (T) phasediagram according to the Clausius-Clapeyron equation. This allows acontrolled melting of the deposition material. By using the pressurechamber, basically every material, can be used for phase-change orthermal printing and spray technique. There is no need for a mask, thepattern is determined by the printing process, i.e. droplets emerging asa jet from nozzles towards the surface or substrate. The nozzles can bepiezo-controlled and moved over the substrate. It is also possible tomove the substrate while the nozzles are fixed. Additionally, evenhigher precision can be achieved by using an integrated shadow mask,e.g. a photo resist, which can be used to determine the patterns.Ultrahigh precision can thus be achieved.

The deposition material can be selected to comprise one of an organicmaterial, an OLED material, biological molecules, nanoparticles, and acombination thereof. Further, the deposition material can be acomposition in form of a powder. This has the advantage that it can beeasily mixed with further components. Moreover, the deposition materialcan be provided as a pellet. This allows a comfortable way of packaging,storing, handling, and processing.

In another embodiment of the present invention, a field-effecttransistor, also referred to as a thin-film field-effect transistor, ismade by a process comprising the steps of forming source and draincontacts on a substrate; heating and applying a pressure to a depositionmaterial to form a melt, the deposition material comprising an organicsemiconducting material; depositing the melted deposition material ontothe substrate with the source and drain contacts by one of aphase-change printing technique, and a spray technique, wherein themelted deposition material solidifies on the substrate and forms anorganic semiconducting layer; forming an insulating layer on the organicsemiconducting layer; and forming a gate contact on the insulatinglayer. It is also possible to form the source, drain, and/or gatecontacts as well as the insulating layer by the phase-change printing orspray technique. This has the advantage that the whole device can befabricated by the presently disclosed process.

Although the present invention is applicable in a broad variety ofapplications it will be described with the focus put on an applicationto an organic electroluminescent device, i.e. an organic light-emittingdevice (OLED) and a field-effect transistor, but first general issuesand the process is addressed. Within the description, the same referencenumbers are used to denote the same parts or the like.

FIG. 1 illustrates a phase diagram of a one-component system. In aconventional physical vapor deposition process the solid material isusually heated at a reduced pressure to a temperature above therespective sublimation temperature to vaporize the material (arrowlabeled with a). When the solid material is heated at a pressure abovethe triple point then the solid changes into liquid phase at therespective fusion point (arrow labeled with b). In the depicted examplefor Anthracene the triple point temperature is 489K, the fusiontemperature at normal pressure is 490K. The phase diagram of two andmore-component systems is by far more complex. The principle of changingfrom solid to liquid phase is still applicable.

FIGS. 2 a-c illustrate steps for forming a pattern on a surface 10 bydeposition of a deposition material 20. For the sake of simplicity, thefigure is simplified to a droplet. Two or more thereof are contemplatedto form a pattern and multiple a layer. FIG. 2 a illustrates thedeposition material 20. As indicated by the arrow and the letters T, P,the deposition material 20 is heated and a pressure is applied within apressure chamber (not shown) to form a melt. The melted depositionmaterial 21 is illustrated in FIG. 2 b. Then, as indicated in FIG. 2 c,the melted deposition material 21 is deposited on the surface 10 by aphase-change printing or spraying technique. Thereby the melteddeposition material 21 solidifies instantaneously when it reaches thesurface 10. The melted deposition material 21 can be deposited via piezoelements (not shown). Finally, as indicated in FIG. 2 c, the solidifieddeposition material 20 remains on the surface 10. In order to depositmultiple or various layers of the deposition material 20 or differentdeposition materials, the process steps are repeated. The depositionmaterial 20 can also be mixed with other materials or may 16 comprise oftwo or more components. In the FIGS. 2 a-c, the symbols “o” illustratethe components of the deposition material 20 in solid form whilst thesymbols “−” illustrate the components of the deposition material 20 inmelted form.

The FIGS. 3 a to 3 c show a schematic illustration of the formation ofan organic light-emitting device (OLED). In at least some instance theOLED includes a thin layer, or layers, of suitable organic materialssandwiched between a cathode and an anode. One suitable example of theOLED is illustrated in FIG. 3 a. On a suitable surface of a substrate100, a first electrode (anode) 102 (metal, ITO, conductive polymer) isprovided either by conventional methods, like PVD, CVD, spin coating orsputtering, or by the phase-change printing technique. The substrate 100can be made of glass, silicon, polymer, or a combination thereof ormight even be a pre-patterned thin-film transistor array. The OLEDfurther comprises a hole transport layer 106 and an electrontransport/emitter layer 110′ and a second electrode (cathode) 112(metal).

Other OLED multi-layer devices may include further layers as depicted inFIG. 3 b. Besides the hole transport layer 106 a hole injection layer104 may be included. The combined electron transport/recombination layercould be separated into an electron transport layer 110 and an emissionlayer 108. All of those layers can be blends of several materials inparticular the emission layer could be a blend of one or several hostand dye materials. Thus, such multi-layer OLEDs can be formed on thesuitable surface by consecutive casting of individual layers by thephase-change printing or spraying technique described with reference tothe FIGS. 2 a-c and FIG. 5.

A display can be formed as illustrated in FIG. 3 c. Red 302, green 304,and blue 306 OLED pixels may be printed on a receptor substrate 300 byphase-change printing or spraying technique. Alternatively, the red,green and blue OLEDs could be printed on top of each other to create amulticolor stacked OLED device.

One example of the formation of a field-effect transistor is illustratedin FIG. 4. Two electrical contacts named source and drain 402 are formedon the surface of an insulating substrate 400 that can comprise glass,silicon, polymer, or a combination thereof. The source and drain 402 canbe formed by conventional techniques, e.g. PVD, CVD, sputtering, etc.,but source and drain 402 can also be formed by phase-change printing orspraying. Further, an organic semiconducting layer 404 is applied byphase-change printing or spraying between source and drain contacts andoverlapping these contacts 402. Pentacene or alpha-sexithiophene canhere be used as organic molecules for the deposition material. Aninsulating layer 406 is then formed over the semiconducting layer 404,thereby the insulating layer 406 can comprise highly insulatingmaterials such as tetrafluorethylen or vinylidenedifluoride derivatives.The polymers thereof are known as Teflon or PVDF (Teflon is a trademarkof E.I. Du Pont de Nemours & Company). Finally, a third electrode 408,the gate electrode, is formed on top of the insulating layer 406. Thethird electrode 408 can be formed like the source and drain 402 and alsomay comprise nanoparticles of gold. The phase-change printing orspraying technique can be applied to all or several layers of thefield-effect transistor. In fact, one printer with various containerseach filled with the respective application or deposition materials canbe used to produce a complete device, like the above-described OLED orthin-film transistor.

FIG. 5 illustrates the phase-change printing principle with its units.The simplified illustration shows a print-head 40 that comprises apressure chamber 42 with the deposition material 20 filled in. Further,the print-head 40 comprises material jets 46 which work, for example,with piezo elements or nozzles (not shown in detail) to eject the melteddeposition material 21. The print-head 40 can be brought close to thesurface 10 of a device or substrate 11. For applying the depositionmaterial 20 to the surface, either the print-head 40 is moved over thesurface 10 or the print-head 40 is fixed and the substrate 11 with thesurface 10 is moved in a way to pattern the surface 10 accordingly. Inoperation, via the material jets 46, the melted deposition material 21is brought to the surface 10 where the melt 21 solidifies immediatelyand the solidified deposition material 20 remains. In a furtherembodiment, a material loader (not shown) containing the depositionmaterial 20 is positioned close to the print-head 40 or even formtogether a single unit. In another embodiment, multiple of the materialloader, each filled with a different deposition material 20, can be usedto support the pressure chamber 42 and the print-head 40.

Any disclosed embodiment may be combined with one or several of theother embodiments shown and/or described. This is also possible for oneor more features of the embodiments. Thus, the invention includesapparatus providing the steps of any process described above employingmeans known to those familiar with the art.

1. A process comprising fabricating an electronic device having apattern formed on a surface by a deposition material, the step offabricating comprising the steps of: heating and applying a pressure tothe deposition material without requiring a solvent to be present toform a melt; depositing the melted deposition material on the surfacewith one of a phase-change printing technique and a spray technique,wherein the melted deposition material solidifies on the surface in asingle phase transition from the melt to a solid.
 2. The processaccording to claim 1, wherein the deposition material is selected tocomprise one of: an organic material an OLED material, biologicalmolecules, nanoparticles, and any combination of these materials,wherein in the step of heating and applying a pressure is performed in apressure chamber, and further comprising repeating the steps of heatingand depositing to deposit multiple layers of the deposition material,wherein the multiple layers are formed by depositing differentdeposition materials.
 3. The process according to claim 1, furthercomprising repeating the steps of heating and depositing to depositmultiple layers of the deposition material.
 4. The process according toclaim 3, wherein the multiple layers are formed by depositing differentdeposition materials.
 5. The process according to claim 1, wherein thedeposition material is selected to comprise one of: an organic material;an OLED material; biological molecules; nanoparticles; and anycombination of these materials.
 6. The process according to claim 1,wherein the deposition material is selected to comprise a composition inform of a powder.
 7. The process according to claim 1, wherein thedeposition material is provided as a pellet.
 8. The process according toclaim 1, used to fabricate one of: an organic light-emitting device; amonochrome and/or color display; a biological pattern; a biochip; asensor; a semiconductor device; and a circuit.
 9. A process forfabricating a field-effect transistor comprising the steps of: formingsource and drain contacts on a substrate; heating and applying apressure to a deposition material without requiring a solvent to bepresent to form a melt, the deposition material comprising an organicsemiconducting material; depositing the melted deposition material ontothe substrate with the source and drain contacts by one of: aphase-change printing technique; and a spray technique, wherein themelted deposition material solidifies on the substrate and forms anorganic semiconducting layer in a single phase transition from the meltto a solid; forming an insulating layer on the organic semiconductinglayer; and forming a gate contact on the insulating layer.
 10. Anapparatus to fabricate an electronic device having a pattern formed on asurface by a deposition material, the process comprising: means forheating and applying a pressure to the deposition material withoutrequiring a solvent to be present to form a melt; and means fordepositing the melted deposition material on the surface with one of: aphase-change printing technique; and a spray technique, wherein themelted deposition material solidifies on the surface in a single phasetransition from the melt to a solid.
 11. The process according to claim1, wherein the means for heating and applying a pressure is performed ina pressure chamber, and further comprising repeating the steps ofheating and depositing to deposit multiple layers of the depositionmaterial, wherein the multiple layers are formed by depositing differentdeposition materials.
 12. An apparatus to fabricate a field-effecttransistor comprising: means for forming source and drain contacts on asubstrate; means for heating and applying a pressure to a depositionmaterial without requiring a solvent to be present to form a melt, thedeposition material comprising an organic semiconducting material; meansfor depositing the melted deposition material onto the substrate withthe source and drain contacts by one of a phase-change printingtechnique, and a spray technique, wherein the melted deposition materialsolidifies on the substrate and forms an organic semiconducting layer;means for forming an insulating layer on the organic semiconductinglayer; and means for forming a gate contact on the insulating layer. 13.The process according to claim 12, further comprising repeating thesteps of heating and depositing to deposit multiple layers of thedeposition material.
 14. The process according to claim 9, wherein thestep of heating and applying a pressure is performed in a pressurechamber.
 15. The process according to claim 14, further comprisingrepeating the steps of heating and depositing to deposit multiple layersof the deposition material.
 16. The process according to claim 15,wherein the multiple layers are formed by depositing differentdeposition materials.
 17. The process according to claim 9, wherein thedeposition material is selected to comprise one of: an organic material;an OLED material; biological molecules; nanoparticles; and anycombination of these materials.
 18. The process according to claim 9,wherein the deposition material is selected to comprise a composition inform of a powder.
 19. The apparatus according to claim 10, wherein thedevice is one of: an organic light-emitting device, a monochrome and/orcolor display, a biological pattern, a biochip, a sensor, asemiconductor device, and a circuit.
 20. The apparatus according toclaim 10, wherein multiple layers are formed by the means for depositingdepositing different deposition materials.